1. Field of the Invention
The present invention relates to a liquid crystal display apparatus. The present invention more specifically relates to a liquid crystal display apparatus which allows excellent viewing angle compensation, which exhibits exceptional contrast in an oblique direction, and which can be reduced in thickness.
2. Description of the Related Art
FIG. 11A shows a schematic sectional view of a conventional liquid crystal display apparatus, and FIG. 11B shows a schematic sectional view of a liquid crystal cell used for the liquid crystal display apparatus. A liquid crystal display apparatus 900 is provided with: a liquid crystal cell 910; retardation plates 920 and 920′ arranged on outer sides of the liquid crystal cell 910; and polarizing plates 930 and 930′ arranged on outer sides of the retardation plates 920 and 920′, respectively. The polarizing plates 930 and 930′ are generally arranged such that respective absorption axes thereof are perpendicular to each other. The liquid crystal cell 910 includes: a pair of substrates 911 and 911′; and a liquid crystal layer 912 as a display medium arranged between the substrates. One substrate 911 is provided with: a switching element (typically, TFT) for controlling electrooptic characteristics of liquid crystal; and a scanning line for providing a gate signal to the switching element and a signal line for providing a source signal thereto (the element and the lines not shown). The other substrate 911′ is provided with: color layers 913R, 913G, and 913B constituting a color filter; and a light shielding layer (black matrix layer) 914. A space (cell gap) between the substrates 911 and 911′ is controlled by a spacer (not shown).
The retardation plates are used for the purpose of optical compensation of the liquid crystal display apparatus. Various attempts have been made at optimization of optical characteristics of the retardation plates and/or at arrangement of the retardation plates in the liquid crystal display apparatus for attaining optimum optical compensation (such as improvement in viewing angle characteristics, improvement in color shift, and improvement in contrast). Conventionally, as shown in FIGS. 11A and 11B, one retardation plate is arranged between the liquid crystal cell 910 and the polarizing plate 930, and another retardation plate is arranged between the liquid crystal cell 910 and the polarizing plate 930′ (see JP 11-095208 A, for example). In order to attain optimum optical compensation with such a structure, the retardation plates disclosed in JP 11-095208 A and arranged on both sides of the liquid crystal cell each have a thickness of 140 μm. However, when conventional retardation plates are used in a liquid crystal display apparatus in a conventional arrangement, contrast in an oblique direction often degrades. Meanwhile, further improvement in screen uniformity and display quality is demanded with recent development of a high-definition and high-performance liquid crystal display apparatus. In consideration of such a demand, degradation of contrast in an oblique direction is a critical issue. Further, a demand for reduction in thickness of the liquid crystal display apparatus has increased with the development of a small, portable liquid crystal display apparatus. However, a liquid crystal display apparatus is hardly reduced in thickness if two thick retardation plates are arranged as in the conventional liquid crystal display apparatus.
As described above, a liquid crystal display apparatus capable of satisfying the demands for excellent display quality and reduction in thickness has been desired strongly.